This invention relates to application to fruit bearing plants of particular agents to induce fruit abscission. The invention is particularly useful where the fruits are citrus fruits, especially oranges.
The ability of plants to slough off organs, such as fruit, by an active separation of cells is described by plant physiologists as the process of abscission. Abscission, unaided by mechanical or chemical agents, results from the formation of a starch-filled layer of cells in the area of the fruit rind separating the stem from the fruit. This starch-filled layer is known as the abscission layer. Abscission occurs as the cells in the abscission layer begin to separate, eventually dropping the fruit from the stem. Abscission generally occurs shortly after the fruit has fully matured.
Commercial harvesting of fruit bearing plants very often requires deviation from the natural abscission cycle. Many varieties of fruit bearing plants, such as citrus, reach maturity and are harvested without completion of the abscission cycle. Moreover, citrus fruit can actually regreen, i.e., become more tightly attached to the fruit stem, as acceptable maturity standards for eating quality are reached.
When fruit is mechanically harvested without chemical aids and the cells of the abscission layer have not begun to separate or the fruit has begun to regreen, a great deal of force is required to remove the fruit. Often when adequate force to remove the fruit is applied to the fruit or fruit bearing plant, a break or tear can take place and a plug of tissue may be removed from the fruit rind; sometimes the fruit stem is broken, leaving a jagged woody stem attached to the fruit; or the fruit bearing plant itself is injured.
Several chemicals have been used to regulate the abscission process of fruit bearing plants in attempts to facilitate harvesting. Such chemicals are called, in general terms, harvesting aids or abscission agents. Typical abscission agents are formulated to loosen fruit at the time of harvest.
Abscission agents disclosed in the patent literature include pyridine-N-oxides (U.S. Pat. No. 3,810,752), alkylamines (U.S. Pat. No. 3,867,127), and hydroxylamines (U.S. Pat. No. 3,869,278).
Abscission agents that are the subject of pending patent applications are bis(2-pyridine-N-oxide)disulfides (Bednarz and Otten, Ser. No. 602,610 filed Aug. 7, 1975 now abandoned; bis(2-pyridine-N-oxide)disulfoxides (Otten and Rheinecker, Ser. No. 602,626 filed Aug. 7, 1975; bis(2-pyridine-N-oxide)disulfones (Otten and Rheinecker, Ser. No. 602,335 filed Aug. 6, 1975) now abandoned; and 1,2-bis(thiomethyl) alkanes and derivatives thereof (Rheinecker, Ser. No. 676,762, filed Apr. 14, 1976 now abandoned).
It is an object of the present invention to provide a method of inducing abscission utilizing agents of different chemical structure from the agents set forth above.
It is an object of this invention in one of its preferred aspects to provide a method of inducing abscission utilizing such agents in combination with non-phytotoxic surfactants.
It is an object of this invention in another of its preferred aspects to provide novel compositions for admixture with water for application to fruit bearing plants to induce fruit abscission.
These and other objects and advantages of the invention will be evident from the following detailed description.